1.Field of the Invention
The invention relates to a method for producing a photodiode contact for a TFA image sensor with a photodiode by depositing a multi-layer system and a transparent, conductive contact layer on an ASIC circuit that has been coated with an intermediate metal dielectric component and that has vias in the pixel grid, which extend through the intermediate metal dielectric component and are each linked with a respective strip conductor of the ASIC circuit, wherein the intermediate metal dielectric component accommodates a barrier layer, which is structured in the pixel grid and carries a CMOS metallization.
2. Discussion of the Related Art
This type of optical component is used to convert electromagnetic radiation into an intensity-dependent photocurrent. Such a TFA sensor (thin-film-on-ASIC sensor) consists of a matricial or linear system of image points (pixels). The electronic circuits for operating the sensor (e.g., pixel electronics, peripheral electronics, system electronics) are usually fabricated using CMOS-based silicon technology, and include an application-specific integrated circuit (ASIC). Separated from it by an insulating layer and connected with it by corresponding electrical contacts, a multi-layer system is arranged on the ASIC as a photodiode, which converts electromagnetic radiation into an intensity-dependent photocurrent. This photocurrent is transferred to specific contacts present in each pixel by means of vias (throughplating) of the underlying pixel electronics (B. Schneider, P. Rieve, M. Böhm, Image Sensors in TFA (Thin Film on ASIC) Technology, ed. B. Jähne, H. Hausecker, P. Geiβler, Handbook of Computer Vision and Applications, pp. 237-270, Academic Press, San Diego, 1999). The multi-layer system based on hydrogenated, amorphous silicon (a-Si:H) that comprises the photodiode consists of a bottom n-type a-Si:H layer, an intrinsic a-Si:H layer and a p-type a-Si:H layer, for example. The transparent, conductive contact layer located on this multi-layer system serves as a front electrode for the photodiode.
Such a multi-layer system is described in “J. A. Theil, M. Cao, G. Kooi, G. W. Ray, W. Greene, J. Lin, A J. Budrys, U. Yoon, S. Ma, H. Stork, Hydrogenated Amorphous Silicon Photodiode Technology for Advanced CMOS Active Pixel Sensor Imagers, MRS Symposium Proceedings, vol. 609, 2000.” The photodiode is here formed by a pin configuration based on amorphous silicon, i.e., by an amorphous silicon layer comprised of a p-conducting, self-conducting (intrinsic) and n-conducting layer sequence. The n-layer is usually the lowermost layer facing the ASIC. The electrical contacts are formed on this side facing the ASIC by a structured metal layer, for example, while the contact on the side facing the direction of incident light is generally established by the transparent and conductive layer.